The M4A1 is a 5.56 mm lightweight carbine that is air-cooled, gas-operated, and magazine-fed. The M4A1 has a semiautomatic or full automatic fire capability and provides personnel with an offensive/defensive capability to engage targets with direct small arms fire. The M4A1 currently implements a gun barrel which is heavier and of larger outer diameter than the M4 standard barrel. The M4A1 heavy barrel was designed and implemented to increase heat dispersion in order to reduce cook off and barrel failure in the M4 carbine due to high temperatures exhibited during high cadence firing. The M4A1 heavy barrel carbine has become an Army standard carbine. The M4A1 helically fluted barrel of this invention was developed to increase heat dispersion and to reduce weight without negatively affecting the reliability and balistic effects of the overall M4A1 system. All rifles and carbines are detrimentally affected by heat. By reducing the heat input into the system or by increasing the rate at which heat can be disipated, the life expectancy and reliability of the rifle/carbine can be improved. The weight that a warfighter must typically carry is also burdensome on his/her ability to operate, thus a rifle/carbine's weight must ideally be reduced to an optimal level that will not affect the operation of the weapon itself. There are several methods by which heat dispersion might be achieved. These include increasing the mass of the heat absorbing material, increasing the surface area of the heat disipating material, cooling of the material through liquids or gasses flowing over the surface of the material, using different materials with more conductive thermal properties, or by reducing the temperature of the gases within the system. Each of these methods have their benefits and detriments with most resulting in the increased weight of the system.
The M4A1 helically fluted barrel of this invention by contrast incorporates multi-start variable pitch helical openings incorporated into the profile of the M4A1 heavy barrel. The helical openings remove material from the barrel outer profile, reducing weight, and also increase the outer surface area for heat dissipation. The advantage of incorporating the multi-start variable pitch helical openings is not only that the weight is reduced and the surface area is increased, but also that the target dispersion and reliability of the system remain unchanged. There is no ‘drooping’ of the barrel (destructive bending) with intense heat, for example. Several prototype M4A1 helically fluted barrels of this invention have been successfully tested with improvements fully demonstrated with regard to, e.g., lower weight, deflection, target accuracy, and heat dispersion characteristics. Further, barrel weight reductions of approximately 0.25 pounds have been successfully accomplished due to these helical openings. Temperatures as high as 909.5 degrees Fahrenheit peak temperature were sustained for the barrel, thus even exceeding current operating amounts.